Discussion and authors' closure of a paper by R D Evans and A C Monteith published in the June 1937 issue, pages 695–705, and presented for oral discussion at the power transmission session of the summer convention, Milwaukee, Wis, June 22,1937

System Recovery Voltage Determination by Analytical and A-C Calculating Board Methods

Shunt capacitor placement in radial distribution networks considering switching transients decision making approach

MAGNIFICATION of transient voltages in one part of an electric power system may occur in another part of that system, possibly at a different voltage level. Experiences such as these have resulted in system flashovers or equipment damage. The degree of voltage magnification does not necessarily involve circuit-breaker restriking or prestriking, although these factors may increase the severity of the disturbance.

Magnification of Switching Surges

Some Fundamentals on Capacitance Switching [includes discussion]

The switching of capacitors differs from other switching by causing relatively large surge currents and possibly overvoltages. The performance of circuit breakers in this service has been found by recent experiments to depend on the power supply system as well as on the size of the capacitor banks. When circuit breakers open with no delayed restriking of the arc, they avoid the possibility of causing undesirably high current and voltage surges.

Capacitor Switching Phenomena

A medium-speed cathode-ray oscillograph with a rotating film has been built for the study of circuit breaker transients. The film is wrapped around a drum and rotated in the vacuum at high speed. Each film shows in a continuous trace a complete story of the formation of arc, subsequent reignitions, and final extinction. More than 15 complete cycles may be recorded without excessive blurring. Each film is self-calibrated. A stutdy of several types of circuit breakers with this instrument shows that the nature of the transients at time of arc extinction varies with the type of breaker on test. Different types of breakers tested on the same circuit have different rates of rise of recovery voltage. The deionizing efficiency of a breaker influences not only the arcing time, but the transient oscillation at current zero. The influence of the deionizing efficiency of the breaker upon the stability of the decreasing arc current near current zero is studied and interesting conclusions made.

Arc Extinction Phenomena in High Voltage Circuit Breakers-Studied With a Cathode Ray Oscillograph

Analyses of cathode ray oscillograms of circuit interruptions reveal characteristics of the circuits that are significant in the study of circuit breaker performance. While a complete analysis of such an oscillogram involves much detailed work, the study of several typical oscillograms reveals the significance of certain types of voltage variations and thus makes possible the analysis of similar oscillograms without detailed measurements. Several oscillograms made on typical laboratory circuits are presented and analyzed in this paper.

Breaker Performance Studied by Cathode Ray Oscillograms

The switching of high-voltage transmission lines and underground cables occasionally produces overvoltage surges on electric power systems. While operating experience generally has been satisfactory voltages of 66 kv and below, there have been transient disturbances of considerable magnitude at the higher voltages. The length of many of the transmission lines and the importance of maintaining continuity of service on heavily loaded interconnections have stimulated a critical analysis of the problem. However, in contrast to the extreme overvoltages predicted by theoretical studies, a review of several hundred field tests over the past ten years, including many tests with voltage records by cathode ray oscillographs, discloses practically no cases of line or bus surge voltages on solidly grounded systems reaching transient peaks as high as 2? times normal line-to-ground crest voltage. This paper attempts to evaluate the effect of both the circuit constants and the characteristics of the various types of interrupters used in modern high voltage oil circuit breakers on the magnitude of switching surges. Particular attention is given to the advantages and disadvantages of such oil flow pistons or low ohmic value resistors in parallel with the main arc extinguishing devices.

R. C. Van Sickle

Papers

Capacitor Switching Phenomena

Arc Extinction Phenomena in High Voltage Circuit Breakers-Studied With a Cathode Ray Oscillograph

Breaker Performance Studied by Cathode Ray Oscillograms

The Interruption of Charging Current at High Voltage

Capacitor-Switching Phenomena with Resistors [includes discussion]